Housing
What size is your tank? 2.5 g
What temperature is your tank? 80 degrees
Does your tank have a filter? Yes
Does your tank have an air stone or other type of aeration? No
Is your tank heated? Yes
What tank mates does your betta fish live with? None

Food
What type of food do you feed your betta fish? TetraBetta pellets, freeze dried bloodworms
How often do you feed your betta fish? Pellets once a day, 1 bloodworm every other day.

Maintenance
How often do you perform a water change? 50% every other day
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change? Water conditioner, stress coat +

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Symptoms and Treatment
How has your betta fish's appearance changed? Yes, he had a small pink spot like he rubbed himself or bumped against something and a scale was missing. Now, 4 hours later the scales are turning dark gray and look to be sticking up slightly.
How has your betta fish's behavior changed? Still pretty active, eating, swimming fine. Just started taking breaks and sitting still along the bottom.
When did you start noticing the symptoms? 4 hours ago
Have you started treating your fish? If so, how? Just so happens I did a 50 % water change about 12 hours ago. Water conditioner and stress coat added. I just added 1/2 tsp aquarium salt.
Does your fish have any history of being ill? Had some fin rot upon purchasing 3 weeks ago. Have been doing 50% water changes every other day, hasn't gotten worse or better.
How old is your fish (approximately)? Bought 3 weeks ago.

Pretty much covered my issues above. Tiny, pink fleshy spot where a scale was missing now looking really bad within 4 hours. Not sure what the problem is or what I should treat it as...bacterial, fungal, etc. Please advise.

I bought some Maracyn 1 & 2 and am treating him now. The wound is now covering half his body :( I have never had something so bad happen so quickly! It looks to have puss or maybe some white stuff coming out of it today and he doesn't really use that right front fin now. How quickly should I expect the meds to start working and know if they'll be enough?

If it looks like that then find Kanaplex and Furan 2 and use both together. I would first do 100% water change with same temp water (match temp using his tank thermometer under the running tap). Rinse everything in the tank really well. Dillute and add the meds for a tank this size + the conditioner. Acclimate him to the new water by floating him in the tank for an hour, while adding a couple tablespoons of the new water to his cup every 10 minutes. Kanaplex will need to be redosed every other day. Furan 2 will need to e redosed daily. I would do a 100% change every other day.